Species Identification and Frequency Characteristic of Japanese Anchovy (Engraulis japonicus) Using Hydro-Acoustics

In this study, the KRM (Kirchhoff-ray mode) model was used to identify the acoustic scattering characteristics of anchovies according to frequency, and the school detection method and dB-difference method were used to identify the acoustic signals of Japanese anchovy on the echogram. The TS (target strength) values of anchovies were checked in the echograms of areas where more than 95% of anchovies were collected to establish frequency range. In addition, the parameter values were set by estimating the size of the anchovy school from the echogram, and the echo signal of the anchovy was identified by school detection using the set parameter values. The results showed that the average TS fluctuations of anchovies were larger for small-sized anchovies (5.5 cm) than for large-sized anchovies (16.9 cm), but TS fluctuations after frequency 130 kHz showed similar trends. Species identification analysis identified only the echo signal of anchovies in the echograms, with depths of 20–70 m for anchovies and 90–110 m for other fish species.